SUBROUTINE SGER(M,N,ALPHA,X,INCX,Y,INCY,A,LDA) * .. Scalar Arguments .. REAL ALPHA INTEGER INCX,INCY,LDA,M,N * .. * .. Array Arguments .. REAL A(LDA,*),X(*),Y(*) * .. * * Purpose * ======= * * SGER performs the rank 1 operation * * A := alpha*x*y' + A, * * where alpha is a scalar, x is an m element vector, y is an n element * vector and A is an m by n matrix. * * Arguments * ========== * * M - INTEGER. * On entry, M specifies the number of rows of the matrix A. * M must be at least zero. * Unchanged on exit. * * N - INTEGER. * On entry, N specifies the number of columns of the matrix A. * N must be at least zero. * Unchanged on exit. * * ALPHA - REAL . * On entry, ALPHA specifies the scalar alpha. * Unchanged on exit. * * X - REAL array of dimension at least * ( 1 + ( m - 1 )*abs( INCX ) ). * Before entry, the incremented array X must contain the m * element vector x. * Unchanged on exit. * * INCX - INTEGER. * On entry, INCX specifies the increment for the elements of * X. INCX must not be zero. * Unchanged on exit. * * Y - REAL array of dimension at least * ( 1 + ( n - 1 )*abs( INCY ) ). * Before entry, the incremented array Y must contain the n * element vector y. * Unchanged on exit. * * INCY - INTEGER. * On entry, INCY specifies the increment for the elements of * Y. INCY must not be zero. * Unchanged on exit. * * A - REAL array of DIMENSION ( LDA, n ). * Before entry, the leading m by n part of the array A must * contain the matrix of coefficients. On exit, A is * overwritten by the updated matrix. * * LDA - INTEGER. * On entry, LDA specifies the first dimension of A as declared * in the calling (sub) program. LDA must be at least * max( 1, m ). * Unchanged on exit. * * * Level 2 Blas routine. * * -- Written on 22-October-1986. * Jack Dongarra, Argonne National Lab. * Jeremy Du Croz, Nag Central Office. * Sven Hammarling, Nag Central Office. * Richard Hanson, Sandia National Labs. * * * .. Parameters .. REAL ZERO PARAMETER (ZERO=0.0E+0) * .. * .. Local Scalars .. REAL TEMP INTEGER I,INFO,IX,J,JY,KX * .. * .. External Subroutines .. EXTERNAL XERBLA * .. * .. Intrinsic Functions .. INTRINSIC MAX * .. * * Test the input parameters. * INFO = 0 IF (M.LT.0) THEN INFO = 1 ELSE IF (N.LT.0) THEN INFO = 2 ELSE IF (INCX.EQ.0) THEN INFO = 5 ELSE IF (INCY.EQ.0) THEN INFO = 7 ELSE IF (LDA.LT.MAX(1,M)) THEN INFO = 9 END IF IF (INFO.NE.0) THEN CALL XERBLA('SGER ',INFO) RETURN END IF * * Quick return if possible. * IF ((M.EQ.0) .OR. (N.EQ.0) .OR. (ALPHA.EQ.ZERO)) RETURN * * Start the operations. In this version the elements of A are * accessed sequentially with one pass through A. * IF (INCY.GT.0) THEN JY = 1 ELSE JY = 1 - (N-1)*INCY END IF IF (INCX.EQ.1) THEN DO 20 J = 1,N IF (Y(JY).NE.ZERO) THEN TEMP = ALPHA*Y(JY) DO 10 I = 1,M A(I,J) = A(I,J) + X(I)*TEMP 10 CONTINUE END IF JY = JY + INCY 20 CONTINUE ELSE IF (INCX.GT.0) THEN KX = 1 ELSE KX = 1 - (M-1)*INCX END IF DO 40 J = 1,N IF (Y(JY).NE.ZERO) THEN TEMP = ALPHA*Y(JY) IX = KX DO 30 I = 1,M A(I,J) = A(I,J) + X(IX)*TEMP IX = IX + INCX 30 CONTINUE END IF JY = JY + INCY 40 CONTINUE END IF * RETURN * * End of SGER . * END